The production of high-quality finished parts having a base of rubber requires exact temperature control within the mold during the vulcanization of such parts. Such a temperature control pre-supposes that equal temperatures can be maintained over the entire surface of the heater plate which is connected to the mold.
However, this requirement is affected by the heat radiation which varies, depending on the size of the plate, at the marginal portions of the heater plate. It has been found to be difficult to counteract such temperature differences without substantial expense. The high pressure acting upon the heater plate during the molding operation also causes a limit for the arrangement of heating elements within the heater plate.
In order to obtain a relatively short time for heating the plate, it is advantageous to install the highest possible heat output which is capable of compensating for the losses of heat in the heater plate. Moreover, such high heating permits regulation of the heating output by zones in a simple manner.